Field of the Invention (Technical Field)
The invention relates to a method for detection of a flaw or flaws in the railway track, and to a rail vehicle to be used in such a method.
Description of Related Art Including Information Disclosed Under 37 C.F.R. §§1.97 and 1.98
A method for detection of rail top defects in a rail-way track by measuring an axle box acceleration signal of the rail vehicle is known from the Dutch patent NL 2 003 351. Such rail top defects are local short vertical geometrical deviations that may cause impact between the rails of the railway-track and the rolling wheels of a rail vehicle. Unless repaired a light rail top defect or squat will grow into a moderate defect, and subsequently into a severe defect. Rail fracture and damages to its fastening, the rail pads, sleepers and ballast (or slab) may ultimately occur if no remedial action is taken.
The invention is concerned with dealing with a broader range of problems than only squats. Railway tracks have a superstructure and a substructure. The superstructure comprises rails, switches and crossings (S & C), insulated joints (IJ), fasteners, sleepers and ballast (or slab). Due to the interaction between the wheels of the train and the track, dynamic forces arise between the wheels and the rails. As a consequence thereof stresses and strains arise in and between the track components, resulting in wear, deformation, and eventually possibly breakdown of the railway superstructure due to (metal) fatigue.
Generally speaking, the dynamic forces cause that the quality and performance of the components and the track system as a whole degrades. The components which are subject to (gradual) degradation include the rails, the switches and crossings, the insulated joints, the rail pads, (loose and missing) fasteners, (damaged or hanging) sleepers. Also local poor ballast and slab quality is a concern.
It is an object of the invention to detect such degradation of the system so that the quality and performance of the components and the system can be restored.
It is a further object of the invention that the detection is performed as early as possible for at least three major reasons: securing safety, avoidance of disruptions and limiting costs. If, for instance, a degradation is detected too late so that a rail break takes place in the switches and crossings, it may lead to derailment and will cause the track to be unavailable for traffic. Passengers' safety is at risk, and passengers' travels will be disrupted or have to be rerouted. Such an unplanned and late repair also results in high costs.
US2007/163352 discloses a method for detection of a flaw or flaws in a railway track, whereby a rail vehicle with rail wheels accommodated to guide the rail vehicle along the railway track is moved along the railway track for exciting the railway into vibration, and wherein the vibrational movement of the railway track surface is measured with a noncontact vibrometer. Conventionally each of the wheels will be connected to the vehicle by an intermediate axle box providing a bearing for the wheels. The rail vehicle is further provided with said non-contact vibrometer which is arranged to measure the vibrational movement of the railway track surface.